In recent years, the development of MEMS devices has been actively made, and such MEMS devices are utilized for optical components such as an optical switch.
As a conventional technology relating to the optical switch using a MEMS mirror as the MEMS device, there has been the following technology. Namely, in a configuration in which an angle of the MEMS mirror is controlled by an electrostatic force generated by applying a drive voltage to thereby lead an input optical signal to a predetermined output position, angle deviation of the MEMS mirror is corrected, based on position information for a branched light of the optical signal reflected by the MEMS mirror or the power of the optical signal (refer to Japanese Unexamined Patent Publication No. 2002-236264).
Among the MEMS devices, there is the one, for example, in which a surface of an electrode is coated by an insulating film, in order to suppress electric discharge (generation of secondary electrons) due to the application of the drive voltage. In the optical switch using the MEMS mirror of such a configuration, since polarization occurs in the insulating film due to the application of the drive voltage, there may be deviation in displacement (angle) of the MEMS mirror relative to the drive voltage. Further, a polarization amount in the insulating film is also changed depending on hysteresis of the drive voltage.
In the above conventional technology, since the angle deviation of the MEMS mirror is regulated based on the power of the branched light of the optical signal reflected by the MEMS mirror or the power of the output optical signal, it is possible to cope with, to some extent, the deviation in displacement (angle) of the MEMS mirror relative to the drive voltage, which occurs due to the polarization in the insulating film.
However, according to the above conventional technology, since the power of the branched light of the optical signal or the power of the output optical signal is detected, an insertion loss by the optical switch is further increased. The insertion loss is one of important characteristics of the optical switch, and in the optical switch, it is desirable to suppress the insertion loss as much as possible.
Further, it is necessary to dispose an apparatus (a sensor or the like) for detecting position information relating to the branched light or the power of the optical signal, and therefore, a problem in cost performance still remains.
Incidentally, the deviation in a displacement amount of the movable body relative to the drive voltage is not a problem limited to the MEMS mirror, but is a problem common to MEMS devices each for driving the movable body by the electrostatic force, of which electrode is coated by the insulating film.